The Autonomous Benthic Explorer (ABE) will be one of two unmanned vehicles used to explore and map hydrothermal vents sites near Papua New Guinea. (Photo by Woods Hole Oceanographic Institution)

The Remotely Operated Vehicle (ROV) Jason will be used to collect rock and fluid samples from the mineral-rich sulfide deposits. (Photo by Tom Bolmer, Woods Hole Oceanographic Institution)

A hydrothermal vent chimney on the East Pacific Rise in the eastern Pacific Ocean. Vents like these exist at mid-ocean ridges on the ocean floor around the world. (Photo by Woods Hole Oceanographic Institution)

News Release

Undersea Vehicles to Study Formation of Gold and Other Precious Metals On the Pacific Ocean Floor

An international team of scientists will explore the seafloor near
Papua New Guinea in the western Pacific Ocean later this month with
remotely operated and autonomous underwater vehicles, investigating
active and inactive hydrothermal vents and the formation of mineral
deposits containing copper, gold and other commercially valuable
minerals.

The cruise is a joint expedition between Woods Hole Oceanographic
Institution (WHOI) and Nautilus Minerals Inc. of Vancouver, British
Columbia, a mining exploration company that holds exploration leases in
the Bismarck Sea within the territorial waters of Papua New
Guinea. Nautilus is the first firm to commercially explore the
ocean floor for economically viable massive sulfide deposits, and is
interested in understanding the size and mineral content of the
seafloor massive sulfide systems.

The joint expedition includes a 32-day WHOI research program funded by
the U.S. National Science Foundation to the Pacmanus vent sites in the
Eastern Manus Basin. The remotely operated vehicle Jason
will be used to survey and map the vent areas around an Ocean Drilling
Program hole drilled in 2000. Nautilus will fund an additional
10-day program to explore and sample the Vienna Woods sulfide prospects
on the Manus Ridge, northwest of the Pacmanus study area.

Geophysicist Maurice Tivey of WHOI will head the 42-day expedition,
which begins July 21 from Rabaul, Papua New Guinea, aboard the research
vessel Melville, operated by
the Scripps Institution of Oceanography. Tivey and geochemists Wolfgang
Bach of the University of Bremen (previously at WHOI) and Jeff Seewald
and Meg Tivey of WHOI will map, collect samples and take
high-resolution images of the seafloor at several locations within the
territorial waters of Papua New Guinea. The cruise ends September
1 at Suva, Fiji.

Tivey and his co-investigators are interested in the geochemistry and
structure of the seafloor and the formation of mineral deposits along
mid-ocean and back-arc ridge systems, where new ocean crust is formed.
The team will use the remotely operated vehicle Jason
and the Autonomous Benthic Explorer (ABE), both developed and operated
by WHOI and veterans of many expeditions to hydrothermal vent sites
around the world.

Two areas will be explored, one in the Eastern Manus Basin in the
Bismarck Sea known as the Pacmanus vent site and the other Vienna
Woods, an area of exposed massive sulfide on the Manus Ridge, a small
mid-ocean ridge spreading center to the northwest of the Pacmanus
site. The Pacmanus site is in 1,700 meters of water (about 4,500
feet), while the Vienna Woods site is in 2,500 meters (about 8,000
feet).

“There are differences in the compositions of hosts rock at the two
areas, as well as differences in the geologic and tectonic settings,”
Tivey, an associate scientist in the WHOI Geology and Geophysics
Department, said. In the Eastern Manus Basin at the Pacmanus
vents, the host rocks are felsic or silica-rich compared to the more
typical mid-ocean ridge basalt found at the Vienna Woods site,
providing a contrast in host rock geochemistry.

“It has been suggested that the difference in the chemistry of
the host rock is reflected in the composition of the sulfide chimneys
and deposits, with deposits hosted in the more silica-rich rocks being
richer in gold and other precious metals” Tivey said. “However,
there are other factors that can affect vent fluid and sulfide deposit
composition. For example, some hydrothermal fluids from back-arc
sites appear to have a signature indicative of a magma chamber source,
with magmatically-derived fluids possibly affecting the hydrothermal
systems.”

The research program is designed to determine what factors may be
affecting vent deposit chemistry, Tivey said. In addition to
sampling the deposits and collecting fresh and altered host rock, the
researchers will collect vent fluids using gas-tight samplers to study
the possible influence of both magmatic volatiles and host rock
composition. They will also map the seafloor, and below the
seafloor using geophysical techniques, to better discern the geologic
history and structure of the sites.

Tivey and other scientists and students from WHOI will be joined by
colleagues from Towson University, University of South Florida,
Bridgewater State College and the U.S. Geological Survey, the
University of Bremen in Germany, Seoul University in South Korea, the
Commonwealth Scientific and Industrial Research Organization (CSIRO) of
Australia, the Geological Survey of Papua New Guinea, the University of
Papua New Guinea, and Nautilus Minerals.

The expedition is funded by the National Science Foundation, Nautilus
Minerals Inc., WHOI and the respective research agencies of the
participants.

Originally published: July 14, 2006

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